A live Asian silver carp caught 9 miles from Lake Michigan this summer originated in the Illinois Waterway south of a series of locks and barriers, according to autopsy results.

According to an analysis by Southern Illinois University, the 4-year-old male fish spent a year in the Des Plaines River watershed before being caught June 22 in the Little Calumet River above the U.S. Army Corps of Engineers electric barriers.

The fish originated in the Illinois/Middle Mississippi River watershed.

The multi-agency Asian Carp Regional Coordinating Committee (ACRCC) released the autopsy results on Aug. 18, roughly a week after the Army Corps released details on a $275 million draft plan to halt the invasive fishes advance by strengthening the Brandon Road Lock & Dam, a choke point in the Chicago Area Waterway System.

The plan calls for halting the upstream advance of bighead and silver through a mixture of noise cannons, water jets and another electric barrier at Brandon Road.

U.S. Sen. Debbie Stabenow, D-Michigan, said the autopsy results indicate that "time is of the essence to both implement a permanent solution and take immediate steps to stop Asian carp from reaching our Great Lakes."

"This is the first time that a live Silver carp has been found this close to Lake Michigan," she said. "Now, we have proof that it went through the Brandon Road Lock and Dam," she said.

The ACRCC said it's not known how the fish got past the barrier defenses 37 miles south of Lake Michigan, but "analysis shows that the fish spent no more than a few weeks to a few months in the stretch of river where it was found."

According to autopsy summary results, "it is not possible to determine whether the fish arrived at its collection location in the Calumet River on its own (breaching the electrical barriers) or if it was illegally transported to the Calumet River."

The 8-pound, 22-inch silver carp was caught by commercial fishermen in a regular carp monitoring spot about two miles below the T. J. O'Brien Lock and Dam.

The capture triggered several weeks electrofishing and contract netting across more than 13 miles of the Calumet River, Little Calumet River and Calumet Harbor. More than 20,000 fish were captured, but no more invasive carp were found.

A pro-shipping group known as UnLock Our Jobs, which has argued the existing electric barriers are sufficient to keep the fish from reaching the Great Lakes, issued a statement calling the autopsy results "concerning," but reiterated its opposition to structural changes to the river system at Brandon Road.

Because no other invasive carp have been found "the lone silver carp appears to be an anomaly," said group spokesperson Lynn Muench.

The Illinois Department of Natural Resources says it plans to continue intensive monitoring of the Chicago waterway system this fall, including commercial fish removal in the Illinois Waterway, sampling around the electric barriers and heightened detection work in the Lockport and Brandon Road waterway pools.

Charlie Wooley, U.S. Fish and Wildlife Service Midwest deputy regional director, said the multi-agency control effort "continues to be coordinated and proactive."

"After more than eight years working in the Illinois Waterway, we're not backing down," he said. "We are going to continue to hold the line against these aquatic invaders."

The invasive carp are considered a threat to a $7 billion Great Lakes sport fishing industry because the voracious fish, which tend to dominate ecosystems they colonize, would out-gobble native species.

The Illinois DNR says the leading edge of adult silver and bighead carp are about 50 miles south Lake Michigan at the Dresden Island Pool in the Illinois River, near the mouth of the Kankakee River west of I-55.

The fish are roughly 10 miles south of the electric barriers, which environmental groups don't consider to be strong enough because studies show that barge traffic can shuttle fish through unharmed.

The Alliance for the Great Lakes, a Chicago-based environmental group, said the autopsy results mean that any "stalling or obstructionism" by the Illinois government "will clearly be placing all of the Great Lakes at significant risk."

"It is critical that all of the solutions put on the table in the U.S. Army Corps of Engineers' recently released Brandon Road Lock & Dam Study - from technology to lock closure - must be examined closely," the group said. "None of these options, including lock closure, should be removed from consideration."